Getting lower pressure with Elite Z oil?

Every fusor and fusion system seems to need a vacuum. This area is for detailed discussion of vacuum systems, materials, gauging, etc. related to fusor or fusion research.
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AllenWallace
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Getting lower pressure with Elite Z oil?

Post by AllenWallace » Sat Nov 23, 2013 5:05 am

How much pressure difference would a typical rotary vane pump achieve if it used Elite Z rather then grade 19 oil?
It's 2X in price, Double distilled synthetic hydrocarbon oil.
The vapor pressure of EZ oil is 10-7 torr compared to 10-5 torr, but does that make a difference in a pump that can only get down to a few millitorr (10-3 torr)?

Doug Browning
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Re: Getting lower pressure with Elite Z oil?

Post by Doug Browning » Sat Nov 23, 2013 11:42 pm

The pump is probably designed for some specific viscosity of oil. If this doesn't match, then it might pump worse or draw more power. On the other hand, is this oil rated for use in a diffusion pump as well? If so, then it might eliminate the problem of mechanical pump oil backstreaming into the diffusion pump (if the diffusion pump oil is compatible with it, not likely with some silicone oil in there).

With some kind of vapor trap in between the mechanical and diff pumps, then it might provide some advantage for high vacuum diff pump operation due to its low volatility causing high absorbtion in the trap. Likely would need to be operating the diff pump with a cryo-trap above it anyway to get down to such low pressures for it to make a difference.

For an RGA (residual gas analyzer), possibly there would be some advantage in using such a further refined oil in the mechanical pump. Its vapor might show up on the RGA as fewer and weaker signal peaks (less obscuring of any actual signal being looked for.)

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